Slant Six Bogging Down!

UPDATE! Still having fuel issues, (or at least that is what I think the problem is) not as bad as it was before the new tank was put in but still laggy. I think it has to to with the fact that the car misfires really bad. It will misfire at idle quite bad, also when I drive but I can't hear it after a certain point, but when I let off the gas I can hear it still misfire. Was wondering if it could be the valves or the fuel pump? Any knowledge would be very much appreciated. The misfiring issue has been continuously getting worse over the past few months.